<?php
/*
*  Module written/ported by Xavier Noguer <xnoguer@php.net>
*
*  The majority of this is _NOT_ my code.  I simply ported it from the
*  PERL Spreadsheet::WriteExcel module.
*
*  The author of the Spreadsheet::WriteExcel module is John McNamara
*  <jmcnamara@cpan.org>
*
*  I _DO_ maintain this code, and John McNamara has nothing to do with the
*  porting of this code to PHP.  Any questions directly related to this
*  class library should be directed to me.
*
*  License Information:
*
*	Spreadsheet_Excel_Writer:  A library for generating Excel Spreadsheets
*	Copyright (c) 2002-2003 Xavier Noguer xnoguer@php.net
*
*	This library is free software; you can redistribute it and/or
*	modify it under the terms of the GNU Lesser General Public
*	License as published by the Free Software Foundation; either
*	version 2.1 of the License, or (at your option) any later version.
*
*	This library is distributed in the hope that it will be useful,
*	but WITHOUT ANY WARRANTY; without even the implied warranty of
*	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*	Lesser General Public License for more details.
*
*	You should have received a copy of the GNU Lesser General Public
*	License along with this library; if not, write to the Free Software
*	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

require_once 'PEAR.php';

/**
* Class for writing Excel BIFF records.
*
* From "MICROSOFT EXCEL BINARY FILE FORMAT" by Mark O'Brien (Microsoft Corporation):
*
* BIFF (BInary File Format) is the file format in which Excel documents are
* saved on disk.  A BIFF file is a complete description of an Excel document.
* BIFF files consist of sequences of variable-length records. There are many
* different types of BIFF records.  For example, one record type describes a
* formula entered into a cell; one describes the size and location of a
* window into a document; another describes a picture format.
*
* @author   Xavier Noguer <xnoguer@php.net>
* @category FileFormats
* @package  Spreadsheet_Excel_Writer
*/

class Spreadsheet_Excel_Writer_BIFFwriter extends PEAR
{
	/**
	* The BIFF/Excel version (5).
	* @var integer
	*/
	var $_BIFF_version = 0x0500;

	/**
	* The byte order of this architecture. 0 => little endian, 1 => big endian
	* @var integer
	*/
	var $_byte_order;

	/**
	* The string containing the data of the BIFF stream
	* @var string
	*/
	var $_data;

	/**
	* The size of the data in bytes. Should be the same as strlen($this->_data)
	* @var integer
	*/
	var $_datasize;

	/**
	* The maximun length for a BIFF record. See _addContinue()
	* @var integer
	* @see _addContinue()
	*/
	var $_limit;

	/**
	* Constructor
	*
	* @access public
	*/
	function Spreadsheet_Excel_Writer_BIFFwriter()
	{
		$this->_byte_order = '';
		$this->_data	   = '';
		$this->_datasize   = 0;
		$this->_limit	  = 2080;
		// Set the byte order
		$this->_setByteOrder();
	}

	/**
	* Determine the byte order and store it as class data to avoid
	* recalculating it for each call to new().
	*
	* @access private
	*/
	function _setByteOrder()
	{
		// Check if "pack" gives the required IEEE 64bit float
		$teststr = pack("d", 1.2345);
		$number  = pack("C8", 0x8D, 0x97, 0x6E, 0x12, 0x83, 0xC0, 0xF3, 0x3F);
		if ($number == $teststr) {
			$byte_order = 0;	// Little Endian
		} elseif ($number == strrev($teststr)){
			$byte_order = 1;	// Big Endian
		} else {
			// Give up. I'll fix this in a later version.
			return $this->raiseError("Required floating point format ".
									 "not supported on this platform.");
		}
		$this->_byte_order = $byte_order;
	}

	/**
	* General storage function
	*
	* @param string $data binary data to prepend
	* @access private
	*/
	function _prepend($data)
	{
		if (strlen($data) > $this->_limit) {
			$data = $this->_addContinue($data);
		}
		$this->_data	  = $data.$this->_data;
		$this->_datasize += strlen($data);
	}

	/**
	* General storage function
	*
	* @param string $data binary data to append
	* @access private
	*/
	function _append($data)
	{
		if (strlen($data) > $this->_limit) {
			$data = $this->_addContinue($data);
		}
		$this->_data	  = $this->_data.$data;
		$this->_datasize += strlen($data);
	}

	/**
	* Writes Excel BOF record to indicate the beginning of a stream or
	* sub-stream in the BIFF file.
	*
	* @param  integer $type Type of BIFF file to write: 0x0005 Workbook,
	*					   0x0010 Worksheet.
	* @access private
	*/
	function _storeBof($type)
	{
		$record  = 0x0809;		// Record identifier

		// According to the SDK $build and $year should be set to zero.
		// However, this throws a warning in Excel 5. So, use magic numbers.
		if ($this->_BIFF_version == 0x0500) {
			$length  = 0x0008;
			$unknown = '';
			$build   = 0x096C;
			$year	= 0x07C9;
		} elseif ($this->_BIFF_version == 0x0600) {
			$length  = 0x0010;
			$unknown = pack("VV", 0x00000041, 0x00000006); //unknown last 8 bytes for BIFF8
			$build   = 0x0DBB;
			$year	= 0x07CC;
		}
		$version = $this->_BIFF_version;

		$header  = pack("vv",   $record, $length);
		$data	= pack("vvvv", $version, $type, $build, $year);
		$this->_prepend($header . $data . $unknown);
	}

	/**
	* Writes Excel EOF record to indicate the end of a BIFF stream.
	*
	* @access private
	*/
	function _storeEof()
	{
		$record	= 0x000A;   // Record identifier
		$length	= 0x0000;   // Number of bytes to follow
		$header	= pack("vv", $record, $length);
		$this->_append($header);
	}

	/**
	* Excel limits the size of BIFF records. In Excel 5 the limit is 2084 bytes. In
	* Excel 97 the limit is 8228 bytes. Records that are longer than these limits
	* must be split up into CONTINUE blocks.
	*
	* This function takes a long BIFF record and inserts CONTINUE records as
	* necessary.
	*
	* @param  string  $data The original binary data to be written
	* @return string		A very convenient string of continue blocks
	* @access private
	*/
	function _addContinue($data)
	{
		$limit  = $this->_limit;
		$record = 0x003C;		 // Record identifier

		// The first 2080/8224 bytes remain intact. However, we have to change
		// the length field of the record.
		$tmp = substr($data, 0, 2).pack("v", $limit-4).substr($data, 4, $limit - 4);

		$header = pack("vv", $record, $limit);  // Headers for continue records

		// Retrieve chunks of 2080/8224 bytes +4 for the header.
		$data_length = strlen($data);
		for ($i = $limit; $i <  ($data_length - $limit); $i += $limit) {
			$tmp .= $header;
			$tmp .= substr($data, $i, $limit);
		}

		// Retrieve the last chunk of data
		$header  = pack("vv", $record, strlen($data) - $i);
		$tmp	.= $header;
		$tmp	.= substr($data, $i, strlen($data) - $i);

		return $tmp;
	}
}
?>
